Divalent Lanthanide Tetraisobutylaluminates: Reactivity and Living Isoprene Polymerization

Abstract

AbstractLanthanide (Ln) tetraisobutylaluminates constitute key components in commercial 1,3‐diene polymerization catalysts, and likewise are the homogeneous rare‐earth‐metal catalysts of prime industrial importance. Discrete divalent rare‐earth‐metal complexes [Ln(AliBu4)2] (Ln=Sm, Eu, Yb) reported here display the first structurally characterized homoleptic metal tetraisobutylaluminates. Treatment of [Ln(AliBu4)2] with C2Cl6gives access to SmII/SmIIImixed‐valence cluster [Sm6Cl8(AliBu4)6] and the YbIIcluster [Yb4Cl4(AliBu4)4], respectively. Reaction with B(C6F5)3leads to hydride abstraction and formation of arene‐coordinated hydroborates such as [Sm{HB(C6F5)3}2(toluene)2]. Complexes [Ln(AliBu4)2] engage in single‐component isoprene polymerization, affording highcis‐1,4 polyisoprenes with narrow molecular weight distributions. Binary [Yb(AliBu4)2]/[HNPhMe2][B(C6F5)4] fabricates polyisoprene in a perfectly living manner. The catalytically active species are scrutinized by NMR spectroscopy.